520 DR LAUDER LINDSAY ON NEW LICHENICOLOUS MICRO-FUNGI. 



Their size varies in the same species, but mostly with age. As to site, they affect 

 the thallus or apothecia, or both ; sometimes the under as well as upper surface of 

 the apothecia. They are, like Torula, more frequent on fertile than sterile lichens. 

 As in Torula and Coniothecium, they are conspicuous where the colour of their 

 host is pale. As in these parasites also, they may be few or numerous, scattered 

 or aggregated, discrete or confluent ; in the latter case becoming maculseform. 

 Externally, they frequently resemble Torula and Coniothecium, or the organisms 

 with which they are apt to be confounded; as well as certain young lichen- 

 apothecia, belonging to the Lecideos, e.g., Abrothallus Smithii and oxysporus. 

 Generally only the base is immersed in the host, but sometimes the body of the 

 peritheciumis immersed, only the apex or ostiole projecting above, or being visible 

 on, the surface of the host. The envelope or perithecium is in all cases the same, 

 consisting of brown cellular tissue; frequently, if not generally, the cells being sub- 

 hexagonal. The Microthelice are sometimes associated with, if not productive of, 

 deformities or degenerations of the thallus or apothecia of the lichens on which 

 they grow (e.g., M. Stereocaidicola, M. Baiomycearia, and the parasite which 

 affects Squamaria saxicola as Torula does Lecanora subfusca). 



Their internal structure varies considerably. Some of them are verrucarioid, 

 in so far as they possess sporidiiferous asci, with or without paraphyses. Where 

 paraphyses exist, they are either very delicate, filiform, more or less indistinct, 

 without thickened or coloured tips; or tbey appear as a mere striated jelly. The 

 asci are frequently saccate, as in Arihonia,; short and broad, not tapering below 

 into a pedicle. 



In another group, no asci, paraphyses, sterigmata, nor basidia, were visible, so 

 that it was impossible to determine whether the contained reproductive corpuscles 

 are to be considered sporidia, spores, stylospores, or conidio-spores. Probably 

 in the majority of cases they are really sporidia contained in asci. 



In a third series, the perithecia are quite sterile, containing no reproductive 

 structure. Some of these parasites may prove to be mere pycnidia analogous to 

 Phoma, Septoria, Diplodia, and Sphceropsis. At least one of the parasites grouped 

 under Microthelia possesses pycnidia in addition to sporidiiferous perithecia, viz., 

 that affecting Thelotrema lepadinum. 



In certain exceptional cases, the same perithecium contained not only 

 sporidiiferous asci, but stylospores and basidia; and in one instance ramose 

 filaments, resembling the hypertrophied sterigmata of many lichen-sperm ogonia* 

 {e.g. the parasites accompanying Verrucaria epidermidis v. analepta, and 

 Lecanora pyracea). Parallel phenomena are the occurrence of sporidia and 

 spermatia in the same perithecia in Verrucaria atomaria and Sphceria Lindsay- 

 ana, as seen by myself, and in a certain section of the Verrucaria? as described 



* Vide p. 516, and foot note f . 



